The proposed invention referred to herein as A SQUARE(trademark), was conceived during many years of applying the theory of a 3-4-5 triangle during the practice of laying out perpendicular lines in the construction industry. Creating a perpendicular line, which is any substantial length (approximately 4xe2x80x2 or greater) requires greater accuracy than a framing square can provide due to its size. It is this need for accuracy that dictates the use of a 3-4-5 triangle using the present invention.
Typical application of the 3-4-5 triangle, prior to this, invention, comprised using two tape measures simultaneously, which required two people to perform the operation with any efficiency. A SQUARE(trademark) is a tool which creates 3-4-5 rigid triangle. Advantageously, the tool folds to a compact state with the sides of the triangle aligned to allow it to be portable and storable. The invention has a wide range of uses in the construction industry for many types of lay out, i.e., framing lay out, masonry lay out, concrete form work, finish carpentry, cabinet installation, construction supervision, ceramic tile layout, VCT tile lay out, etc. Furthermore, the design of A SQUARE(trademark) gives it the ability to function as a proficient sheet rock square by resting the three foot leg on the ground rather than the traditional sheet rock square which hangs from the board. The invention may also be produced in a variety of sizes and configurations for example, an isosceles triangle.
Among the prior art patents of general interest are U.S. Pat. Nos. 124,22  124,222 ; 778,659; 1,394,088; 2,667,697; 3,345,750 and 4,955,141. The prior art patents are not directly in  on point and fail to provide an anticipation of the features which have made this invention a great success.
This invention relates to layout tools and particularly to tools providing a right angle for laying out perpendicular lines of any substantial length. The invention comprises three legs or members, all of which are permanently attached at pivot points. Two of the three points are precisely located pivot points. The third point is a precisely located resilient locking stud or rivet which slides in a skewed slot and permits the adjoining two members to slide into a parallel plane to one another in a compact folded position when not in use and then into a locked open position creating a perfect 3-4-5 triangle for layout purposes when in use. Critical to the design is the fact that the manner in which the members are connected and aligned guarantees a perfect and not distorted 3-4-5 triangle. This is crucial to maintain the accuracy of the tool.
Accordingly, an object of this invention is to provide a new and improved layout tool which provides a right angle.
Another object of this invention is to provide a new and improved layout tool which includes a 3-4-5 triangle to provide an accurate 90xc2x0 angle for layout purposes.
A further object of this invention is to provide a new and improved layout tool involving a relatively large 3-4-5 triangle which readily slides into a compact form with the legs of the triangle in a substantially parallel plane.
A more specific object of this invention is to provide a triangular right angle layout tool for laying out perpendicular lines wherein the legs are pivotally mounted to one another at their ends and one end includes a spring-loaded rivet which slides in a skewed slot in an adjacent leg to collapse the triangle into linearly parallel legs.